davis



Aug. 18, 1942. w. l.. DAvls PUMP . Original Fi1 ed-Jne 23, '1939 i5Sheets-Sheet 1 INVENTOR.

BY W. LDAVIS ATTOR NE Y6 Re. 22,160 i W. L. DAVIS Aug. 18,- 19,42.

PUMP

Original Filed June 23. 1959 s sneet's-shiet 2 INVENTOR, BY W.L.Dw1sl.

ATTO R NEY' 18, .1942. I w. l.. DAvls PUMP sheets-sheet s Original FiledJune 25, 1939 FIG' 10 INVENTOR.

VII/.DAVIS om, M QM/ A-r-roreA/EYJ I Reissues Aug.1s,1942

Re. l22.160

UNITED STATES- PATENT oFFlcE l gzltll: 28 1941 Serial No. 280,828, June23, 1939. lApplication for reissue November 28., 1941, Serial No.

7 Claims. (Cl. 10S-138) This invention relates to a rotary pump having aplurality of rigid sliding vanes of constant length and has for itsprincipal object the provision of a pump which will produce an even nowof liquid through the pump without producing pronounced or appreciablepulsations in the flow.

One of the objections to rotary pumps of this type has been that the:dow of liquid through the pump has caused pulsations of varyingmagnitude depending upon the shape and'desgn of the pump bore and, insome cases, upon the ratio of bore diameter to rotor diameter.

The invention contemplates the use of a pump bore of such shape anddesign as to practically eliminate this objectionable feature. Myimproved pump comprises a pump body having a cavity formed therein whichis provided with an inlet port and an outlet port, together withV soshaped as to produce a sliding movement of the vanes within the rotorand longitudinally of themselves of uniform velocity when the rotor isrotated at uniform angular velocity. Thecircular arcs are true segmentso! a circle the radii.

of which are struck from the same center point,

which center point is the center of rotation of the rotor. The portionsof the pump bore which connect with the circular arcs are so constructedas to provide an even running clearance for a. solid vane having alength equal to the sum of the radii of the two circular arcs. The pumpvanes are slidably mounted in the rotor and rotate about the centerpoint of rotation of the rotor. The displacement oi? the pump dependsupon the volume of liquid displaced by the vanes v traveling through thecircular section of the bore esI any point in this section o! the boreis equidistant from the center of rotation so that there can be nosubstantial variation in the volume oi liquid displaced. Thenon-circular or generated portions ofy the pump bore may produce asubstantial variation in the displacement, if not properly constructedor generated. There will portions of the bore if v the vanes do notrecede or slide back into the rotor a uniform distance u,

for each degree of rotation of the rotor. In other words, the vanessliding back into the rotor having the effect of decreasing thedisplacement of the pump and if this rate oi recession of the vanes isnot at uniform velocity there will be pronounced pulsation in the iiow.

In the preferred embodiment of the invention the formula used forlocating any point within the generated portions of' the boreA whichwill produce a urnform rate oi .recession of the vanes is the same asthe mathematical formula for an Archimedes spiral. It will therefore beseen that the non-circular portions of the pump bore are portions of anArchimedean spiral of common foci. In orderl to provide va smooth flownonpulsating pump oi this character, it is preferable to provide a pumpbore the shape of which is a combination ofv two arcs of circles havingdifferent radii struck from the samecenter point of rotation anddiametrically opposed to each other and joined on either side by.complementary shaped portions in the form of Archimedean spirals theequation for which is (r==a0), the

shape of such spirals being governed by the difference between the radiiforming the circular vportions of the bore and the extent of theportions of the spirals .employed being determined by the angles formedby the blades.

Iwo or more `vanes may be used depending upon the specic design of thepump and the work which it is -intended to do. It is possible andusually most desirable to design a pump bore such that the two portionsof circular arcs-are interposed between the angle iormed by one pair of`vanes only, thus in a three-vane pump the angle of the circular arcwould be or in a four-vane pump the angle of .the circular arc would be45 neglecting the thickness of the vanes. It is also possible lto designa pump bore so that the angles of the circular arcs are interposedbetween twice the angle formed by one pairof vanes in which case thelength of the vcircular arc for ya three-vane pump would be 120 and fora fourlvane pump 90. The advanv tage oi a four-vane pump is that therewill be two vanes disposed in the working portion or the bore whichwould have the effect of reducing the slip which would ordinarily get byone vane working in the same portion ofthe bore. IThe three-bladedpumpwould have the'objection over the four-bladed pump that the generatedportions of the bores will impart a rapid sliding be a variation indisplacement in the generated movement to the vaneam The pump vanes maybe made with or without packing stripsor rockers on the ends thereof,whichever design would tend toward more etilcient operation for theparticular service required for the pump. In Iany case, the curvature ofthe non-circular portions of the bore should be such that, for eachdegree of movement of 'the rotor, the pump vanes will slide through therotor a uniform distance so that the volume increase or decrease of anypump chamber is constant,

Further and more limited objects of the invention will appear as thedescription proceeds and by reference to the accompanying drawings inwhich Fig. 1 is a longitudinal vertical sectional view of the pump; Fig.2 is a vertical sectional view of the pump body taken at right angles-tothe view shown in Fig. 1; Figs. 3, 4 and 5 are views in side elevatlonofthe pump blades; Fig. 6 is a view in elevationof one of the pump blades;Fig. 7 is a somewhat diagrammatic view showing a two-bladed pump, withthe inlet and outlet ports indicated in dotted lines; Fig. 8 is a viewsimilar to Fig. 7 showing a three-bladed pump; Fig. 9 is a view similarto Fig. 8 showing a three-bladed pump; and Fig. l is a diagrammatic viewillustrating the pump bore with the.

rotor shown in dotted lines.

Referring now to the drawings, the reference character I designatesgenerally the pump body having a cavity formed therein defining aworking chamber and provided with an inlet 2 and an outlet 3. Rotatablymounted in the pump and eccentrically disposed within the cavity is arotor 4 in which are slidably mounted a-plurality of rigid vanes 5, 6and "I, the opposite ends of which are recessed and received thereinrock- 'ers 8, The vanes and rockers together provide pump blades whichare of constant length and have contact at the opposite ends thereofwith the walls of the pump cavity. 'Ihe rotor has an outwardly extendingshaft portion 9 which is journaled inthe pump body in bearings I0 andII. Disposed at each side of the bearings are leather packing members I2and I3 which are held in place by metal cages I4 and I5. Surrounding therotor shaft adjacent the inner end thereof is a steel disk I6 theperipheral edge of which is bent outwardly and receives therein a rubberwasher or disk l1. Disposed over the rubber washer Il is a steel ring I8which is urged against the rubber washer by a plurality of springsdisposed within recesses provided in the body of the rotor, one of whichis shown at I9. A suitable bore or passageway 20 is provided in the bodyof the pump through which any excess lubricant may escape. The outer endof the rotor shaft is recessed as shown at 2I and is adapted to beconnected with any suitable source of power. 'I'he outer end of the pumpcavity is closed by a removable plate 22 which is secured in place bybolts 23. The pump cavity has a cross section which is made up of a pairof circular arcs A and B, each less than a semicircle and struck from acommon center C, and two adjoining oppositely disposed complementaryshaped arcs D and E the opposite ends of which are disposedsubstantially but not exactly tangent to the circular arcs. The circulararcs are true segments of a circle which is struckfrom a common center Cwhich center point is the center of rotation of the rotor. Thenon-circular or generated portions of the pump bore which -connect withthe circular arcs are so constructed as to provide an even runningclearance for-the vanes which have a length equal to the sum of theradii of the two circular arcs. These noncircular or generated portionsof the pump bore are complementary portions of an Archimedean spiral vofcommon foci. The curvature of the non-circular portions of the pump boreshould be such that, for each degree of movement of the pump there willbe a constant displacement of liquid and the vanes will be caused toslide through the rotor at a uniform velocity upon rotation of therotor.

The size of the inlet and outlet ports is determined by the number ofblades. In Fig, 7 there is disclosed somewhat diagrammatically atwo-bladed pump in which the inlet port extends from the point 24 to`the point 25, while the outlet port extends from the point 2E to thepoint 21. Each working chamber of the pump as it approaches thedischarge position will contain the same volume of liquidand the vaneswill recede into the rotor a uniform distance for each degree ofrotation oi the rotor. 'I'he volume increase or decrease of any pumpchamber, due to the sliding of the .vanes in the rotor, is constant anduniform.

In Fig. 8 there is diagrammatically disclosed a three-bladed pump. Thecircular portions of the pump bore are indicated by the referencecharacters A and B' and the length of the inlet port is the distancefrom the point 24a to the point 25, While the length of the dischargeport is the distance between the points 26a and 21a. The non-circularportions of the pump bore are lindicated by the reference characters D'and E and extend over an arc of 60.

In Fig. 9 there is diagrammatically disclosed a three-bladed pump inwhich the circular portions of the pump bore are indicated by thereference characters A2 and B2, while the generated or non-circularportions of the bore are indicated by the reference characters D2 andE2. The length of the inlet port is the distance between p the points:a4b and ish and the length of the quitlet port is the distance betweenthe points 26h and 212. In the form of pump disclosed in Fig. 9 thecircular portions A2 and B2 extend over an arc of 120.

In Fig. 10 there is disclosed a diagrammatic illustration of the pumpbore for a three-vane pump. The circular portions of the pump bore areindicated by the reference characters A and B' and the non-circular orgenerated portions of the bore are indicated by the reference charactersD and E'. The circular arc A' extends over an arc of 60 and the circulararc B likewise extends over an arc of` 60. The non-circular portions Dand E' connect with the circular arcs A' and B at the oppositefendsthereof. The non-circular portionsD' and E' are complementary portionsof an Archimedean spiral.

It will. be seen that in the three-bladed pump shown in Fig. 9 there aretwo adjacent working chambers discharging one after the other so thatany slippage past one blade of the pump will escape into the nextsucceeding chamber. In the two-bladed pump the length of each of thecircular arcs A and B is whereas in the threebladed pump shown in Figs.8 and 9, the lengths of the circular arcs are 60 and 120l respectively.

It will also be seen that irrespective of the number of blades or vanesused, the pump bore is made up of a pair of oppositely disposedconcentric circular sections each less than a semicircle and twoadjoining oppositely disposed complementary curved sections the oppositeends of which are disposed substantially but not exactly tangent to theadjoining circular sections and so shaped as to produce a slidingmovement of the vanes within the rotor at such a rate that each workingchamber of the pump will contain the same volume of liquid when itreachesthe dischargey position and that the vanes slide through therotor at a uniform and constant velocity when the rotor is rotated atuniform angular velocity. In ,order to obtain this action and toaccomplish the desired result, it is necessary that the non-circular orgenerated portions of the pump bore be complementary portions of anArchimedean spiral disposed as illustrated.

It is of course to be understood that the pump vanes may be used with orwithout packing strips or rockers at the ends thereof, depending uponthe particular work .for which the pump is designed. Various changes maybe made in the details of construction such as in the manner of mountingthe rotor without departing from the spirit of this invention, as thecrux of the invention resides in the particular pump bore of such shapeand curvature that the pump Vanes recede into the rotor at uniformvelocity upon rotation of the rotor at constant speed, the result beinga pump which will have uniform displacement without pulsations. Theinvention is limited only in accordance with the scope of the appendedclaims.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed.

I, therefore, particularly point out and distinctly claim as myinvention:

1. A pump comprising a pump body having a cavity formed therein andprovided with an inlet port and an outlet port, a rotor rotatablymounted in said cavity eccentrically thereof, not more than two bladesextending diametrically through the rotor and having a working fit withthe walls of said cavity and dividing the same into a plurality ofworking chambers, said cavity having a cross section made up of twoconcentric circular arcs of different radii each less than a semi-circleand two adjoining curved sections which are complementary portions of anArchimedean spiral of common foci, the ends of said curved sectionsbeing each approximately but not exactly tangent to said circular arcsat the points of their intersection whereby each of said blades as ittravels over the non-circular portion of the cavity will slide throughsaid rotor a uniform distance foreach degree of rotation of said rotor,said rotor fitting the circular arc of lesserradius.

2. A pump comprising a pump body having a cavity formed therein andprovided with an lnlet port and an outlet port, a rotor rotatablymounted in said cavity eccentrically thereof. not more than two bladesextending diametrically through the rotor and having a working fit withthe walls of said cavity and dividing said cavity into a plurality ofworking chambers, said cavity having "a cross section made up of twoconcentric circular arcs of `different radii, each less than asemi-circle and two adjoining curved sections which are complementaryportions of an Archimedean spiral of common foci, the ends of saidcurved sections being each approximately 'but not exactly tangent tosaid circular arcs at the points of their intersection, whereby each ofsaid blades as it travels over the non-circular portion of-the cavitywill slide through said rotor at a constant velocity when the rotor isrotated at uniform angular velocity, said rotor fitting the circularvarc of lesser radius.

3. A pump comprising a pump body having a cavity formed therein andprovided with an inlet andan outlet port, a rotor rotatably mounted insaid cavity and eccentric thereto, not more than two blades extendingdiametrically through the rotor and having a working nt with the wallsof said cavity and dividing said cavity into a plurality of workingchambers, said cavity` having a cross section made up of two concentriccircular arcs of different radii, each less than a semi-circle and twoadjoining curved sections which are complementary portions of anArchimedean spiral cf common foci, the ends of said curved sectionsbeing each approximately but not exactly tangent to said circular arcsat the points of their intersection whereby each of said blades as ittravels over the non-circular portion oi' the cavity will slide throughsaid rotor at a constant velocity when the rotor is rotated at uniformangular velocity, the opposite ends of each of said blades beingrecessed and a 'rocker received in each of said recesses, the vanes androckers together having a length equal to the sum of the radii of thetwo circular arcs, said rotor fitting the circular arc of lesser radius.

4. A pump comprising a pump body having a cavity formed therein andprovided with an in-` let port and an outlet port, a rotor rotatablymounted in said cavity, eccentrically thereof,

three lor more blades extending diametrically through the rotor andhaving a working fit with the walls of said cavity and dividing saidcavity into a plurality of working chambers, said cavity having a crosssection made up of two concentric circular arcs of different radii eachless than a semi-circle and two adjoining curved sections Which arecomplementary portions of an Archimedean spiral of common foci, the endsof said curved sections being each approximately but not exactly tangentto said circular arcs at the points of their intersection whereby eachof said blades as it travels over the non-circular portion of the cavitywill slide through said rotor a uniform distance for each degree ofrotation of said rotor, said rotor fitting the circular arc lof lesserradius.

5. A pump comprising a pump body having a cavity formed therein andprovided with an inlet port and an outlet port, a. rotor rotatablymounted in said cavity, eccentrically thereof, three or more bladesextending diametrically through the rotor and having a working iit withthe walls of said cavity and dividing said cavity into a plurality ofworking chambers, said cavity having a cross section made up of twoconcentric circular arcs of different radii each less than a semi-circleand two adjoining curved sections which are complementary portions of anvArchimedean spiral of common foci, the ends of said` curved sectionsbeing each approximately but not exactly tangent to said circular arcsat the points of their intersection whereby each of said blades as ittravels over the non-circular portion of the cavity will slide throughsaid rotor a uniform distance for each degree of rotation of said rotor.

(i. A pump comprising a pump body having a cavity formed therein andprovided with an inlet port and an outlet port, a rotor rotatablymounted in said cavity, eccentrically thereof,. a plurality of `bladesextending diametrically through the rotor and having a. working t with`the walls of said cavity and dividing said cavity into a plurality ofworking chambers, said cavity having a cross section made up o! twoconcentric circular arcs of diierent radii each less than a, semi-circleand two adjoining curved sections which are complementary portions ot anArchimedean spiral of common foci, the ends of said curved ,sectionsbeing each approximately but not exactly tangent to said circular arcsat the points oi' their intersection whereby each of said blades as ittravels over the non-circular portion of the cavity will slide throughsaid rotor a uniform distance for each degree of rotation of said rotor.

7. A pump comprising a pump body having a cavity formed therein andprovided with an inmounted in said cavity, eccentrically thereof, a

` let port and an outlet port, a rotor rotatably plurality of bladesextending diametricaily through the rotor and having a. working nt withthe walls oi' said cavity and dividing said cavity into a plurality ofworking chambers, said cavity having a cross section made up of twoconcentric circular arcs of diierent radii each less than a senil-circleand two adjoining curved sections vwhich are complementary portions ofan Archimedean spiral of common foci, the ends of said,

curved sections being each approximately but not exactly tangent to saidcircular arcs at the points oi' their intersection whereby each of saidblades as it travels over the non-circular portion of the cavity willslide through said rotor a uniform distance tor each degree of rotationVoi' said rotor, said rotor titting the circular arc of lesser radius.

WALWIN L. DAVIS.

